1. Field of the Invention
The present invention relates generally to apparatus for removably attaching one item to another and more specifically to apparatus for attaching labels to surfaces. One application of the invention is apparatus by means of which function strips may be attached to the keyboards used with typewriters, word processors, computer terminals, and similar devices.
2. Description of the Prior Art: FIG. 1
Originally, keyboards were part of mechanical devices such as typewriters. In such devices, the functions which a given key performed remained unchanged for the life of the device. As the devices with which the keyboards were used became first electrical and then electronic, the relationship between a key and the function it performed became changeable. For example, electric typewriters often have removable type elements. On one occasion, the type element may contain a Latin alphabet and a given keystroke will produce a given Latin letter; on another, it may contain a Greek alphabet and the same keystroke will produce a given Greek letter. When keyboards are used with programmable devices, the relationship between a key and the function it performs may vary from program to program, and in many cases, the user himself may program the key to give it a private meaning. Indeed, programmable keys became so important with computers that keyboards for use in computer systems often contained one or more rows of special function keys above or to the sides of the main alphanumeric keyboard.
As it became possible to change the functions performed by keys, keyboard users and makers developed various methods of indicating what a key meant at a given time. Users taped labels onto keys and makers provided detachable key caps. After one or more rows of programmable function keys became a regular feature of keyboards in computer systems, users began using function strips to identify the functions which the programmable function keys represented during execution of a given program. FIG. 1 shows a keyboard 101 with such a function strip 103. As may be seen from that figure, function strip 103 is simply a strip of labels which indicate the current meaning of a row 105 of keys functioning as programmable function keys.
The first function strips 101 were simply strips of tape which users placed above or below a row of function keys 105; later, system manufacturers and program makers provided users with cardboard templates. The templates were cut out so that they would fit over the row of function keys; when a user executed a program, he put the template for the program over the function keys and could tell what functions the keys had in that program from the template. Finally, the makers of keyboards began incorporating provisions for attaching function strips 103 into their keyboards 101. Among these provisions were channels or brackets above or below function keys 105 into which the user oould slide a function strip which he made for himself or received with a program. Another such provision was buttons on the keyboard and slits in the function strip which permitted the function strip to be "buttoned" to the keyboard.
As keyboard users have begun to routinely use programs having different sets of function keys, the need has increased for function strips which can be securely mounted and are tidy, but which may be rapidly changed. Further, users are now able to shift rapidly back and forth between programs, and cannot be expected to change function strips each time they change programs. Consequently, it is no longer enough to be able to attach a single function strip to the keyboard, and the technique used to attach the function strips must provide for several such strips.
None of the prior art techniques is completely adequate for the needs of present-day keyboard users. Tape function strips are untidy and hard to change. Function strips attached by channels, brackets, or buttons have several disadvantages: first, the function strips are hard to change; second, the channels and buttons remain even if no function strips are being used and detract from the appearance of the keyboard; third, in the case of channels or brackets, the width of the space required for the channel or bracket is greater than the width of the function strip, and thus requires that keyboards be wider than is required for the function strip alone. Template function strips, finally, while easy to change, are untidy and tend to fall off the keyboard; furthermore, only one template function strip can be used at a time with a row of function keys 105. As will be explained in more detail below, the present invention solves the the problems of prior-art function strip attachment techniques by providing a technique which is tidy, provides a secure attachment, takes up little space, permits easy change of function strips, permits more than one function strip, and which does not detract from the appearance of the keyboard when no function strips are being used.